Since the structure of a surface layer of a solid differs substantially from the structure of the solid in the bulk and in many respects governs its behavior in different media and in the fields of various forces, the information on the surface layer of a solid opens up the way to the scientifically-based modification of the surfaces of solids with the purpose of obtaining materials with desirable optical, mechanical, adhesive, electrical, luminescent and other properties, as well as to the control of many processes important in the practical respect, such as crystal growth, epitaxial and plasma chemical growth of layers, catalysis, preparation of ultrathin film structures by the Langmuir-Blodgett and molecular self-assembly techniques, strengthening of materials, etc. It also allows one to control the surface quality (surface defectoscopy) of industrial products with a higher precision, which is especially important in such fields as protective coatings and micro/nano electronics.
Methods for analyzing physical properties of solids, in particular temperatures and activation energies of phase and relaxation transitions in materials, by means of differential scanning calorimetry (see V. A. Bershtein, V. M. Egorov, “Differential Scanning Calorimetry in Physics and Chemistry of Polymers”, “Khimiya”, Leningrad, 1990, pp. 74-81) and by means of nuclear magnetic resonance (see Ya. Rabek, “Experimental Methods in Polymer Chemistry”, v. 1, Moscow, “Mir”, 1983, p. 337) are known.
A disadvantage of these methods is that they mainly characterize the properties of the sample bulk and do not give proper information on the sample surface layer.
A technique for analyzing physical properties of the surface layer of a solid, in particular determination of temperatures and activation energies of phase and relaxation transitions, involving surface bombardment with primary beams of neutral atoms and/or electrons and/or ions and/or photons and/or X-rays and detection of secondary beams of the corresponding charged particles (see, for example, A. Gzanderna “Methods of Surface Analysis”, Moscow, “Mir”, 1979, pp. 63-64, 76-77, 83-84, 88-89 (a copy of the pages referred to is attached)) is known.
This technique is taken as a prototype of the variant of the method as per claim 1 of the present invention.
When the surface layer of a solid is probed (bombarded), charged particles (electrons, ions), neutral particles (atoms, molecules), and photons are emitted. The surface layer is investigated under constant bombardment, the quantity, energy and spatial distribution (angles of departure) of the emitted particles being detected. However, said method that involves continuous bombardment of the surface gives rise to undesirable modifications of the surface layer investigated. Moreover, since the experiment is typically carried out at a constant temperature of a solid, this method cannot give information on temperatures and energies of phase and relaxation transitions in the surface layer; if the experiments are performed on one and the same sample at several temperatures, the sample surface undergoes multiple bombardments, which results in even more severe changes of the sample surface and, hence, in unreliable transition parameters.
A method for analyzing physical properties of the surface layer of a solid is known, involving the activation of the surface layer of a solid by low-temperature plasma (LTP) followed by deactivation of the surface layer during which a thermoluminescence spectrum is recorded. The LTP used in this method is ignited by an unmodulated voltage with a frequency of 40.68 MHz at a 10-Pa pressure of a plasma-generating gas, the duration of the sample activation by LTP being from 10 s to 9 min (see A. A. Kalachev, etc., “Plasma-induced Thermoluminescence—a New Method for Investigating Supramolecular Architectures and Temperature Transitions in Polymers and Other Solid Surfaces”, Applied Surface Science 70/71 (1993), pp. 295-298 (a copy is attached)).
This engineering solution is taken as a prototype of the variant of the method as per claim 3 of the present invention.
The disadvantage of the prototype method is a modifying influence of the LTP with said parameters upon the surface layer of the sample investigated, which results in insufficiently reliable information on physical and chemical properties of this layer. First of all, this is due to strict plasma parameters used in the prototype, namely, a high pressure of a plasma-generating gas (10 Pa) and relatively long (10 s and more) duration of plasma activation. Both factors lead to overheating of the surface layer and a decay of arising active states already in the course of plasma treatment. For example, as seen from FIG. 4 of the prototype, the luminescence intensity typically falls with increasing treatment time. Moreover, said strict plasma parameters lead to other physical-chemical changes in the surface layer being analyzed.
In addition, in the mode of isothermal luminescence (see FIG. 3, paper by A. A. Kalachev etc.) the curves obtained according to the known method and illustrating the dependence (decrease) of thermoluminescence on time from the moment the LTP activation of the sample is over have no characteristic features; therefore, during this period of time no useful information on the surface structure or surface physical-chemical processes was obtained using said method. The curves are only used as a means for the determination of the moment when heating aimed at deactivation of the surface layer of a solid has to be started.